Haiku's 64bit port is progressing nicely. "As you can see, this looks pretty much like a regular Haiku desktop. There's still a lot of things missing, though - not many apps or drivers yet. However, most things should be fairly simple to get working, typically just a few compilation fixes."

Back in the days, PhosphorOS introduced basic multi user support. Also an (officially unreleased) ZETA 1.51 also supported multi-user support. I cannot recall experiencing incompatibilities with these implementations.

Note: PhosphorOS' implementation was not really secure: hitting control-alt-delete, killing the login task, and then clicking restart desktop gave you a desktop as the default 'baron' user. But this was experimental, and besides, PhosphorOS was a BeOS distro, so based on closed source software. (I think it was Dan0 based)

Was it ctri+alt+delete? That sounds like a Windows shortcut. BeOS never had an inbuilt task manager.

Dano (Dan0 doesn't exist, Dano0 does, Dano was the designation, Dano0 was part of the build name, as was Maui0 for R5 and Genki0 for R4.5) source was leaked. Yellow tab had it. This is all pretty clear.